Clutch driven aircraft electric taxi system and method

ABSTRACT

A clutch driven aircraft electric taxi system is provided with a clutch assembly designed to be automatically selectively engaged or disengaged as required to drive an aircraft autonomously during ground operations. The clutch assembly is mounted integrally with other electric taxi system components completely within an aircraft landing gear wheel and may be designed with one way overrunning or selectable clutch engagement capability in one or both rotational directions, preferably using an arrangement of ratcheting struts and clutch elements adapted specifically for use in an aircraft landing gear drive wheel environment. The clutch assembly may automatically disengage in response to predetermined defined conditions or operating parameters. A failsafe overrunning capability ensures that the clutch assembly will not engage taxi system drive components so that an aircraft&#39;s wheel will not be driven during aircraft operation when safety considerations dictate that the aircraft electric taxi system should not be engaged.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.14/932,342, filed 4 Nov. 2015, which claims priority from U.S.Provisional Patent Application No. 62/075,849, filed 14 Nov. 2014, thedisclosures of which are fully incorporated herein.

TECHNICAL FIELD

The present invention relates generally to aircraft electric taxisystems and specifically to a controllable clutch driven aircraftelectric taxi system designed to selectively engage an electric taxisystem to drive an aircraft during ground operations and a method forselectively and safely operating a clutch driven aircraft electric taxisystem.

BACKGROUND OF THE INVENTION

As air travel has increased over the past decades, airport facilitieshave become more crowded and congested. Minimizing the time between thearrival of an aircraft and its departure to maintain an airline's flightschedule, and also to make a gate or parking location available withoutdelay to an incoming aircraft, has become a high priority in themanagement of airport ground operations. The safe and efficient groundmovement of a large number of aircraft simultaneously into and out oframp and gate areas has become increasingly important. As airline fuelcosts and safety concerns and regulations have increased, the airlineindustry is beginning to acknowledge that continuing to use anaircraft's main engines, even at low thrust settings, to move aircraftduring ground operations is no longer the best option. The delays,costs, and other challenges to timely and efficient aircraft pushbackfrom airport terminals associated with the use of tugs and tow vehiclesmakes this type of aircraft ground movement an unattractive alternativeto the use of an aircraft's main engines to move an aircraft on theground. Restricted use of an aircraft's engines on low power duringarrival at or departure from a gate is an additional, althoughproblematic, option. Not only does such engine use consume fuel, it isalso burns fuel inefficiently and produces engine exhaust that containsmicroparticles and other products of incomplete combustion. Operatingaircraft engines, moreover, are noisy, and the associated safety hazardsof jet blast and engine ingestion in congested gate and ramp areas aresignificant concerns that cannot be overlooked.

The use of landing gear motors and drive systems to drive aircraftautonomously during ground operations has been proposed by applicantsand others, and a range of such motors and systems is described in theart. U.S. Pat. No. 7,469,858 to Edelson; U.S. Pat. No. 7,891,609 to Cox;U.S. Pat. No. 7,975,960 to Cox; and U.S. Pat. No. 8,109,463 to Cox etal., owned in common with the present invention, describe aircraft drivesystems that use electric drive motors to power aircraft wheels and movean aircraft autonomously on the ground without reliance on aircraft mainengines or external vehicles. U.S. Pat. No. 3,807,664 to Kelly et al.and U.S. Pat. No. 7,445,178 to McCoskey et al. describe aircraft wheeldrive systems that use, respectively, hydraulic or electric motors todrive aircraft during taxi. U.S. Patent Application Publication Nos.US2009/0294577 to Rogues et al; US2010/0206980 to Cros et al.;US2011/0304292 to Charuel et al.; and U.S. Patent ApplicationPublication No. US2012/0104158 to Charles et al. additionally describevarious aircraft drive devices and motors controllable to move aircraftduring ground operations. While the use of coupling elements or clutchesis suggested in some of the foregoing aircraft wheel drive systems, itis not suggested that these coupling elements or clutches could bestructured or function to automatically avoid engagement of the wheeldrive system when the system should not be engaged, nor is it suggestedthat coupling element or clutch function could or should be enabled atdefined drive modes, speeds, or other operating parameters.

U.S. Patent Application Publication No. US2010/0065678 to Kiyosawadescribes a self-propelled wheel apparatus with a coaxially linkedmotor, wave gear, and a one-way clutch to drive an aircraft on theground. The clutch in the Kiyosawa system, however, is stated totransmit rotational force to move the aircraft only in a reversedirection and to cause the wheel to rotate only when the aircraft movesbackward. Such a clutch design could not function effectively to enableaircraft autonomous movement during all ground operations, includingtaxiing or movement in both forward and reverse directions, betweenlanding and take off.

Automotive and like vehicle clutch assemblies that may be selectivelyengaged or disengaged are well known in the art. U.S. Pat. No. 3,075,623to Lund; U.S. Pat. No. 3,599,767 to Soderquist; and U.S. Pat. No.7,661,329 to Cali et al., for example, describe clutch assembliesincorporating sprag or pawl elements that may transmit torque betweenraces or rotatable elements depending, in part, on their relativedirections of rotation. One way vehicle clutches designed to lock in onedirection and allow free rotation in the opposite direction are alsoavailable, as are improved selectable one way clutch designs, such asthose described in U.S. Pat. No. 6,290,044 to Burgman et al.; U.S. Pat.No. 7,980,371 to Joki; and U.S. Pat. No. 8,042,670 to Bartos et al.Various other selectable clutch designs that provide controllableoverrunning and coupling functions in automotive automatictransmissions, are described in U.S. Pat. No. 8,079,453 to Kimes and inU.S. Patent Application Publication Nos. US2010/0252384 to Eisengruber;US2011/0233026, US2013/0062151, and US2014/0102848 to Pawley;US2013/0277164 to Prout et al.; and US2014/0116832 to Beiser et al.While these clutch designs may function effectively in an automotivewheel environment, an aircraft landing gear drive wheel environment issignificantly different and poses safety and other considerations thatdo not accompany the operation of automotive and like vehicles. Neitherthe foregoing clutch designs nor other commonly available clutch designsare sufficiently robust to function effectively and reliably in anaircraft landing gear drive wheel environment. It is not suggested thatany of the foregoing clutch designs may be adapted to selectively andautomatically transfer torque as required during operation of anaircraft electric taxi system in response to selected operating or otherparameters. Nor is it suggested that these clutch designs are or couldbe adapted to avoid engagement of a drive system when it should not beengaged. Moreover, the clutches noted above do not provide the kind offailsafe capability that ensures that the clutch will never beengageable during flight, landing, takeoff, or during any other aircraftoperating condition when operation of an electric taxi system would beunsafe.

A need exists for a clutch assembly adapted to function effectively andsafely in an aircraft landing gear drive wheel drive system environmentas an integral component of an aircraft electric taxi system. Aadditional need exists for a clutch assembly designed to automaticallyand selectively engage a drive motor to transfer torque and drive anaircraft drive wheel and move the aircraft autonomously on the groundonly at predetermined speeds or operating conditions and/or in selecteddrive modes in a desired direction. A need also exists for a clutchassembly designed with a failsafe capability ensuring that the clutchassembly will never be engageable to activate the electric taxi systemwhen aircraft operating conditions indicate that system operation isunsafe.

SUMMARY OF THE INVENTION

It is a primary object of the present invention, therefore, to providean aircraft electric taxi system with a clutch assembly adapted tofunction effectively and safely in an aircraft landing gear drive wheeldrive system environment as an integral component of an aircraftelectric taxi system.

It is another object of the present invention to provide an aircraftelectric taxi system with a clutch assembly designed to automaticallyand selectively engage a drive motor to transfer torque and drive anaircraft drive wheel and move the aircraft autonomously on the groundonly at predetermined speeds or operating conditions and/or in selecteddrive modes in a desired direction.

It is an additional object of the present invention to provide anaircraft electric taxi system with a clutch assembly designed to fitcompletely within the operational profile of an aircraft landing geardrive wheel that is operatively coupled to taxi system components toautomatically and selectively transfer torque to system components onlywhen required to drive the drive wheel and move the aircraftautonomously in a commanded direction during taxi.

It is a further object of the present invention to provide an aircraftelectric taxi system with a clutch assembly with one way selectableclutch elements integrally coupled to an aircraft drive wheel drivesystem mounted within an aircraft landing gear wheel that automaticallytransfers torque through drive system components selectively whenrequired to engage drive system components or to disengage drive systemcomponents in response to predetermined operating parameters.

It is a further object of the present invention to provide an aircraftelectric taxi system incorporating a clutch assembly with a failsafeoverrunning capability designed to ensure that the taxi system is neverengaged when the aircraft is in flight, during landing or takeoff, andat other times when the taxi system should not be operational.

In accordance with the aforesaid objects, a clutch driven aircraftelectric taxi system is provided. The electric taxi system includes aclutch assembly that is designed to selectively and controllablytransfer torque to system components to drive an aircraft autonomouslyduring ground operations only in response to predetermined system oraircraft operating parameters and conditions in a desired direction. Theclutch assembly is mounted integrally with other electric taxi systemcomponents completely within defined space available in an aircraftlanding gear wheel where the clutch assembly can be selectively engagedand/or disengaged as required. The clutch assembly may be designed withone way overrunning or selectable clutch engagement capability in one orboth rotational directions, preferably using an arrangement ofratcheting struts and other clutch elements adapted specifically for usein an aircraft landing gear drive wheel environment. The clutch assemblymay be designed to operate differently when rotating in a forwarddirection or drive mode than in a reverse direction or drive mode. Theclutch assembly additionally may have the capability to automaticallydisengage in response to predetermined defined conditions or operatingparameters, for example motor speed or drag detected outside suchdefined conditions or parameters. A failsafe overrunning capabilityensures that the clutch assembly will not engage taxi system drivecomponents so that an aircraft's wheel will not be driven when theaircraft is in flight, during landing and takeoff, and at other timesduring aircraft operation when safety considerations dictate that theaircraft electric taxi system should not be engaged.

Other objects and advantages will be apparent from the followingdescription, claims, and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagrammatic view of a clutch drivenaircraft electric taxi system in accordance with the present inventionmounted in an aircraft landing gear wheel; and

FIG. 2 is a cross-sectional diagrammatic view of a portion of a clutchassembly showing the main elements in a prior art controllable orselectable clutch assembly that may be adapted to controllably drive anaircraft landing gear electric taxi system to move an aircraft duringground operations.

DESCRIPTION OF THE INVENTION

The benefits of being able to efficiently and safely move an aircraftduring ground operations without reliance on the aircraft's main enginesor external vehicles have been recognized. Actually achieving thesebenefits, however, has proved challenging. Applicant's previouslyproposed aircraft electric taxi systems have been demonstrated toeffectively power drive wheels and move aircraft on the ground and,thus, can enable aircraft operators to achieve the many advantages ofautonomous ground movement. The present invention improves thecapabilities of Applicant's original aircraft electric taxi system andexpands the advantages possible when aircraft can be driven autonomouslyduring ground operations independently of the aircraft's main enginesand external ground vehicles. These advantages and improvements areachieved, in large part, by the design of an aircraft electric taxisystem that incorporates a clutch assembly, selectively engageable asdescribed herein, to transfer torque and control operation of theelectric taxi system as required to safely drive an aircraft landinggear wheel and move the aircraft during taxi.

“Aircraft electric taxi system,” as used herein, refers to a system ofaircraft drive components, including an electric drive motor to providemotive force, typically mounted with an aircraft nose or main landinggear wheel and designed to drive the aircraft nose or main landing gearwheel and move the aircraft autonomously during taxi and other groundoperations without operation of an aircraft's main engines or assistancefrom external tow vehicles.

Referring to the drawings, which are not necessarily drawn to scale,FIG. 1 shows, in cross-sectional diagrammatic view, a clutch drivenaircraft electric taxi system in accordance with the present inventionmounted within an aircraft landing gear wheel 10. The outboard portionof the wheel is in the direction of the arrow A, and the inboard portionof the wheel is in the direction of the arrow B. For clarity, anoutboard portion of the wheel's tire mounting structure, which may be ademountable flange, and a tire are not shown. The aircraft's landinggear piston and associated inboard structures are also not shown. Thewheel 10 is mounted for rotation about an axle 12. An interior space orrecess 14 defined within the inboard and outboard extent of the walls ofthe wheel 10 may accommodate all of the components of the electric taxisystem. The electric taxi system components include an electric drivemotor 16, which typically has a stationary stator element 18 and arotating rotor element 20, and a drive system 22. A clutch assembly 24may be positioned between the drive system and a wheel section 26adjacent to the axle 12. A clutch input 28 may activate the drive system22. The relative arrangement of components shown in FIG. 1 is only onepossible arrangement. Other arrangements of motor components, drivesystem, and clutch are also contemplated to be within the scope of thepresent invention.

An electric motor preferred as a component of the clutch driven electrictaxi system of the present invention is an electric motor that may beany one of a number of suitable designs. For example and withoutlimitation, a high phase order electric motor of the kind described incommonly owned U.S. Pat. Nos. 6,657,334; 6,838,791; 7,116,019; and7,469,858, the disclosures of the aforementioned patents being fullyincorporated herein by reference, may be effectively used for electrictaxi of an aircraft. A range of other motor designs, whether with aninner rotor as shown in FIG. 1 or with an outer rotor relative to astator, capable of high torque operation across a desired speed rangethat can drive an aircraft landing gear wheel to move an aircraftautonomously on the ground may also be suitable and are contemplated tobe within the scope of the present invention.

The drive system 22 may be a system of gears or another type of drivesystem capable of transmitting torque from a clutch input 28 between aclutch assembly, such as clutch assembly 24, and a motor 16. A rollertraction type of drive system that is designed to actuate an electricdrive motor capable of moving a commercial sized aircraft on the groundnot only may have a low profile and be light weight, but it may alsoprovide the high torque and high speed change ratio required tooptimally operate the motor to move an aircraft on the ground. Eithertype of drive system may be effectively used in the clutch drivenelectric taxi system of the present invention, and these and other typesof drive systems are contemplated to be within the scope of the presentinvention.

The clutch assembly 24 preferred for the present clutch driven electrictaxi system may have overrunning and one way clutch operation featuresand must be sufficiently robust to function to automatically andselectively transfer operational torque in an aircraft landing gearenvironment to components of a drive system designed to drive anaircraft landing gear wheel and move an aircraft during groundoperations. Engagement of the clutch assembly must be avoided orprevented when it should not be engaged. A suitable clutch assemblyshould also be automatically disengageable to physically separatecomponents of an electric taxi system from other aircraft functions sothat these components do not impact such aircraft functions as landing,taxiing, take off, flight, and the like. The clutch input 28, forexample, must automatically disconnect from any torque transferringcontact with the drive system 22 whenever the electric taxi systemshould not be operational. Additionally, a preferred clutch assemblymust enable forward drive and reverse drive up to predetermined definedmaximum speeds for each drive mode. These predetermined defined maximumforward and reverse speeds may be determined based on aircraft type,drive system components, and other factors.

A preferred clutch assembly for a clutch driven electric taxi system inaccordance with the present invention must also be able to preventaircraft ground speed from slowing at any forward speed when the clutchassembly is operating in a forward drive setting or drive mode. When theclutch assembly is operating in a forward drive setting, without acommanded disconnection from an active drive mode at a speed less than apredetermined defined maximum speed, an overrunning function must beenabled when the predetermined defined maximum speed is exceeded.Further, when aircraft speed exceeds a second defined maximum speedgreater than the predetermined maximum speed, the clutch mustautomatically disengage completely. In this case, the clutch input 28would not be in contact with the drive system 22.

When an aircraft is to be driven in reverse, the electric taxi system,and the clutch assembly, must be specifically enabled to drive theaircraft in reverse. The default drive mode is forward. The reversedrive mode is activated only when this is commanded, with reverse drivemode activation designed to be achieved as reliably as possible.

It is contemplated that the clutch assembly may be automaticallyengageable and disengageable in response to a simple electronic command,for example that provided by a solenoid type of activation in responseto sensors and/or actuators associated with the clutch assembly.Although automatic operation of the clutch assembly is preferred, theclutch assembly may also be engaged and disengaged manually, ifnecessary. A commanded wheel spin in a reverse direction mayadditionally be used to disengage the clutch assembly.

The clutch assembly 24 is designed to be an integral component of theelectric taxi system of the present invention, and the electric taxisystem is configured to be fitted completely within the dimensions ofthe space defined within the inboard and outboard boundaries of anaircraft landing gear wheel. Therefore, the clutch may be easily removedand replaced when the electric taxi system is removed and replacedduring routine or other maintenance.

While it is contemplated that a preferred location for the clutch drivenelectric taxi system described herein may be within one or both aircraftnose landing gear wheels, this clutch driven electric taxi system mayalso be installed within other aircraft wheels, including main landinggear wheels.

A preferred clutch assembly that meets the aforementioned requirementsto automatically, effectively, and safely drive an electric taxi systemto move an aircraft during ground operations may include clutch elementsthat enable the clutch assembly to function as a controllable selectableone way clutch with an overrunning capability. While Means Industries,Inc. of Saginaw, Mich. has supplied clutches that may achieve thesefunctions to the automotive industry, this type of clutch assembly hasnot heretofore been proposed or adapted to be integrated into anaircraft electric taxi system to actuate system components and drive anaircraft landing gear drive wheel to drive the aircraft during groundoperations. As noted above, the design considerations for automotive andaircraft landing gear clutch assemblies differ significantly. Forexample, the speed of clutch assembly components in an aircraft electrictaxi system are orders of magnitude greater than in automotive or likevehicular applications and would require a “super” overrunning functionnot present in available clutches. The drag created on clutch componentsat such speeds, moreover, would produce unacceptable wear on struts andother clutch elements.

A clutch assembly contemplated for driving an electric taxi systemaccording to the present invention may lock in one direction whileallowing free rotation in an opposite direction. Torque is transferredfrom a driving element to a driven element during rotation of theelements. Typically, an overrunning clutch assembly permits torquetransfer while permitting free wheeling motion of a driving memberrelative to a driven member when torque transfer is interrupted. Aclutch assembly may include a clutch element referred to as a pocketplate, with recesses or “pockets” in a planar surface that hold springbiased torque transmitting struts or pawls and a notch plate withopenings or notches corresponding to the locations of the pockets whenthe pocket plate and notch plate are aligned. The struts may be heldbelow the pocket plate planar surface to permit rotation of the notchplate or other rotating clutch elements and spring biased to projectabove the pocket plate planar surface to engage a corresponding notch inthe notch plate, thereby causing the pocket plate and notch plate torotate together at the same speed. Centrifugal force produced duringrotation may overcome the spring force of the biasing springs at a setspeed, causing the struts to disengage from the notch plate notches andpermitting the pocket and notch plates to rotate relative to each otherand the struts to ratchet against the notch plate or related structures.A clutch assembly may also include a control plate positioned betweenthe pocket plate and the notch plate configured to cover selectednotches and prevent engagement of the struts at the selected locations.

FIG. 2 illustrates a diagram of a cross section of a portion of a priorart clutch assembly 40 adapted to drive an aircraft electric taxi systemaccording to the present invention. The clutch assembly may include apocket plate 42 and a notch plate 44 with respective coupling faces 46and 48. At least one of the pocket plate 42 or the notch plate 44rotates about an axis, such as wheel axle 12 in FIG. 1, in a directionindicated by arrow C. The coupling face 48 of the notch plate 44 has aplurality of spaced recesses or pockets 50, only one of which is shown,each of which may include a load-bearing shoulder 52. The coupling face46 of the pocket plate 42 has at least one recess 54 with a load-bearingshoulder 56. A strut or pawl 58, which functions as a locking element,is shown biased into engagement with the notch plate shoulder 52 by aspring 60 located in a small recess 62 below the recess 54. The strut 58is moveable between the locked position engaging the shoulder 52 of thenotch plate pocket or notch 50 and an unlocked position in which thestrut 58 occupies the recess 54 and does not extend above the face 46 ofthe pocket plate 42. A control plate 68, which may be in the form of anapertured selector plate with at least one opening 70, is positionbetween the pocket plate 42 and the notch plate 44. The control plateoperates to cover or uncover a selected notch 50, blocking or permittingaccess to the notch by a strut 58. As the control element rotates, eachstrut applies force on the control element produced by the force of thespring 60 biasing the strut 58 toward the control plate.

The strut 58 shown in FIG. 2 is shown in an engaged position that willprevent the relative rotation of the pocket plate 42 and the notch plate44. The entire clutch assembly will rotate in the direction of the arrowC. Rotation of the pocket plate 42 or the notch plate 44 in a directionopposite to that of arrow C will cause the strut 58 to ratchet againstthe edge of the notch 50 opposite the shoulder 52.

The arrangement of clutch assembly elements shown in FIG. 2 is meant tobe illustrative and not limiting. A clutch that is safe and effectivefor driving an aircraft electric taxi system may include some or all ofthe elements shown or additional elements that have been specificallyadapted for optimal function in driving an aircraft electric taxi systemthat meets the requirements described above. For example, struts mayhave a different configuration and may be biased by one or more springsor other elements. The biasing force exerted by one or more springs tomove a strut into locking engagement with a notch plate may be set to beovercome by centrifugal force at a defined rotational speed to preventengagement and to reduce drag and associated wear on struts and otherstructures.

It is contemplated that a suitable clutch assembly may operateautomatically so that complete disengagement may occur automatically. Itis further contemplated that sensors may be used to provide informationsuch as motor speed measurements and to compare this information withwheel speed or other information that may be used to determine whetherautomatic disengagement of the clutch assembly elements is required.Strut springs, for example, could be automatically activated ordeactivated by solenoids or the like to move struts into or out ofengagement with a notch plate. As indicated above, there are situationsin which an electric taxi system should never be engaged, and the clutchassembly can be controlled automatically to ensure that the system isdisengaged and remains disengaged during these situations.

A suitable clutch assembly for the present invention may retain at leastsome manual operation. For example, when an aircraft is to be driven ina forward direction by a clutch driven electric taxi system, the clutchassembly may be designed to be not selectable with a one-way override.When the aircraft is to be driven in a reverse direction, a differentmechanism may be more appropriate. Additionally, automatic operation ofthe clutch may be used to drive an aircraft in a forward direction,while manual operation to positively activate the clutch assembly isrequired to drive the aircraft in a reverse direction. Reversing anaircraft would require pilot operation of the clutch assembly to drivethe electric taxi system to move the aircraft in a desired reversedirection. It is contemplated that suitable cockpit controls may beprovided to permit manual operation of the clutch assembly by anaircraft's pilot or cockpit crew.

Engagement and disengagement of the clutch assembly 24, 40 could betargeted to the speed of the aircraft wheel 10 and/or to speeds ofelectric taxi system components, including the speed of the motor 16and/or drive system 22, as well as to predetermined environmental orother conditions. It is preferred that the present clutch drivenelectric taxi system include one or more failsafe mechanisms, such as,for example, a failsafe overrunning capability in the clutch assembly24, 40, to prevent the clutch assembly from transferring torque toengage or actuate the drive system 22 when the aircraft landing gearwheels are not supporting the aircraft on the ground, such as, forexample, when the aircraft is in flight and at other times when anaircraft landing gear wheel should not be driven. The clutch assemblydescribed herein may be adapted to be selectively engaged in bothforward and reverse rotational directions, as well as with a failsafeoverrunning capability to safely drive an aircraft electric taxi system.

It is further contemplated that a clutch assembly as described above maybe actuated by a hydraulic actuator, an electromagnetic actuator, or anyother actuating system available for this purpose that may beautomatically or manually controlled to produce a control force toengage or disengage, as appropriate, an aircraft drive wheel drivesystem to transmit drive torque to the system as required to drive theaircraft in a forward or reverse direction during movement on a groundsurface.

It is preferred that the various plates, struts, biasing springs, andother components of the clutch assembly described above haveconfigurations and be made of materials designed to withstand hightorque loads, preferably torque loads in excess of a determined maximumtorque load likely to be encountered by an aircraft electric taxi systemand that the materials are demonstrated to be capable of effective longterm operation in an aircraft or aerospace environment.

While the present invention has been described with respect to preferredembodiments, this is not intended to be limiting, and other equivalentarrangements and structures that perform the required functions arecontemplated to be within the scope of the present invention.

INDUSTRIAL APPLICABILITY

A clutch driven aircraft electric taxi system with a selectivelyengageable and controllable clutch assembly designed to safely drive anaircraft electric taxi system to move an aircraft autonomously duringground operations will find its primary applicability where it isdesired to realize the benefits of controlling movement of an aircraftsafely and efficiently on the ground without reliance on the aircraft'smain engines or external ground vehicles.

The invention claimed is:
 1. A clutch driven aircraft electric taxisystem for moving an aircraft autonomously during ground operationscomprising: a. an aircraft landing gear wheel rotatably supporting awheel drive system on an axle completely within a space defined byinboard and outboard boundaries of the wheel; b. an electric taxi drivesystem configured to generate and transmit torque required to drive thelanding gear wheel and move the aircraft autonomously during groundoperations, comprising an electric motor and a drive system in actuatingtorque transfer contact with said electric motor; c. a selectivelycontrollable clutch assembly in torque coupling contact with said drivesystem, said clutch assembly comprising at least a torque couplingelement and a plurality of engagement elements structured to beautomatically engageable or disengageable in response to predeterminedoperating parameters and conditions of said electric taxi drive systemand said aircraft during ground operations, wherein said predeterminedoperating parameters and conditions comprise aircraft speed, aircraftforward drive mode, aircraft reverse drive mode, and an aircraft defaultdrive mode; and d. automatic and manual controls in controlcommunication with said clutch assembly to engage said torque couplingelement and said plurality of engagement elements only when saidelectric taxi system may be safely operated to move said aircraft on theground.
 2. The system of claim 1, wherein said clutch assembly furthercomprises a first rotatable element and a second rotatable element, andeach of said plurality of engagement elements is supported in a recesson said first rotatable element and controllably spring biased to engagea correspondingly positioned notch in said second rotatable element totransfer torque from said clutch assembly to said drive system or not toengage said correspondingly configured notch in said second rotatableelement, preventing torque transfer from said clutch assembly to saiddrive system.
 3. The system of claim 1, wherein said clutch assemblycomprises a one-way clutch assembly or a selectable clutch assembly. 4.The system of claim 1, wherein said drive system comprises a system ofgears or a roller traction drive system.
 5. The system of claim 1,wherein said clutch assembly is coupled in automatically controllabletorque transfer relationship with said drive system to be engageable ordisengageable when said predetermined operating parameters of saidelectric taxi drive system and said aircraft are reached or exceeded. 6.The system of claim 5, wherein said clutch assembly is configured to beautomatically controllable when the aircraft is in a forward drive modeand only manually controllable when the aircraft is in a reverse drivemode.
 7. The system of claim 1, wherein said clutch assembly furthercomprises a clutch input element movable out of torque coupling contactwith said drive system when said clutch assembly is in an overrunningmode.
 8. The system of claim 1, further comprising an automaticallyactivatable failsafe control in said automatic controls in controlcommunication with said clutch assembly, with said torque couplingelement, and with said plurality of engagement elements.
 9. The systemof claim 1, wherein said aircraft default drive mode is forward drive.10. The system of claim 3, wherein said first rotatable elementcomprises a pocket plate with said recesses in a planar surface of saidpocket plate each holding an engagement element comprising a strut orpawl spring biased to project above said planar surface, said secondrotatable element comprises a notch plate with said correspondinglypositioned notches, and said strut or pawl engages said correspondingnotch when said pocket plate and said notch plate are aligned.
 11. Thesystem of claim 10, further comprising a rotatable control platepositioned between said pocket plate and said notch plate configured tocover selected notches and prevent engagement of said struts or saidpawls at said selected notches.
 12. The system of claim 1, wherein saidclutch assembly further comprises a first rotatable element and a secondrotatable element comprising, respectively, a planar pocket plate and aplanar notch plate, each of said plurality of engagement elementscomprises a controllably spring biased strut or pawl supported in arecess in said planar pocket plate and positioned to engage acorresponding notch in said planar notch plate and a rotatable controlplate interposed between said planar pocket plate and said planar notchplate to selectively prevent engagement of said strut or pawl inselected notches.
 13. The system of claim 1, wherein said clutchassembly is positioned between said drive system and a section of saidaircraft landing gear wheel adjacent to said axle.